Repetitive movements such as jogging or running training can induce injuries. Running injuries have been analysed and reported by Knutsen and Hart in chapter 22 of “Epidemiology of Sports Injuries”, ed. D. Caine et al., Human Kinetics, 1996. There is some consensus that injuries develop gradually, i.e. a cumulative effect of repetitive loading, however severe training sessions may also exacerbate an injury. A common injury is knee pain, however injuries of tendons such as the Achilles tendon or posterior tibial tendonitis, plantar fasciitis, pes planovalgum, metatarsalgia and calcaneal spurs, adductor strain, iliofibial band friction syndrome, iliotibial strain, tibial stress syndrome, patello-femoral pain, ankle sprain, back pain especially lower back pain and sciatica, hip or groin pain, thigh pain, foot sprain, and bursitis, have also been reported.
To alleviate these effects it has been proposed to correct training errors, correct muscle imbalance, identify and correct structural abnormalities, correct running style, use running shoes, identify injury early, treat the injury early, prescribe and use orthotics, etc. To achieve these a physical examination of the person is recommended including an identification and assessment of kinetic chain dysfunction as well as identification of previous injuries and measurement of anthropometric and functional characteristics associated with risk of running injury.
A wide variety of diagnostic methods are available to the doctor, e.g. CT-scan, X-ray, MRI scan as well as physical examination. However these are usually carried out in a static mode. There remains a need for a method of identifying potential injuries as well as to diagnose the cause of existing injuries which is easy to use, requires equipment which need not be in a clinic or hospital and which need not be operated by trained medical staff.
U.S. Pat. No. 4,267,728 discloses an apparatus for analysing the foot comprising television cameras for photographing the gait of the subject and for photographing the plantar surface of the foot through a transparent platform. The platform comprises beams each of which is supported at each end by means for detecting load imposed on each beam. The apparatus also includes circuitry for determining the centre of pressure applied to each beam. The centres of pressure and the video outputs from the cameras are displayed on a suitable display.
A further apparatus is known from WO 95/31933 using a walking belt. During a constant walking phase pressure sensors are used to determine the dynamic pressure effect of the feet together with the change in relative position of selected parts of the body by two-dimensional angle measurements and a muscle potential measurement. Also the gait is monitored by video cameras.
U.S. Pat. No. 4,813,436 describes another system for motion analysis comprising markers secured at various joints as well as pressure sensitive shoes or insoles. The subject is photographed during motion using two video carriers. The gait, the angular position of the various joints and other information indicative of walking characteristics are displayed.
These known methods require the use of cameras with each patient to be examined which is complex and expensive. An additional problem with cameras and complex equipment is that it tends to distract the patient and movements may be carried out in an abnormal manner. Hence there is a need to provide equipment for analysing gait which is simple and unobtrusive. Still a further problem is that interpretation of the copious and complex data is difficult even for trained doctors and orthopaedic specialists.